Re: [PATCH] util/log: do not close and reopen log files when flags are turned off

[Richard Henderson <richard.henderson@linaro.org>]

On 10/25/22 19:21, Paolo Bonzini wrote:
> log_append makes sure that if you turn off the logging (which clears
> log_flags and makes need_to_open_file false) the old log is not
> overwritten.  The usecase is that if you remove or move the file
> QEMU will not keep writing to the old file.  However, this is
> not always the desited behavior, in particular having log_append==1
> after changing the file name makes little sense.
> 
> When qemu_set_log_internal is called from the logfile monitor
> command, filename must be non-NULL and therefore changed_name must
> be true.  Therefore, the only case where the file is closed and
> need_to_open_file == false is indeed when log_flags becomes
> zero.  In this case, just flush the file and do not bother
> closing it, thus faking the same append behavior as previously.
> 
> The behavioral change is that changing the logfile twice, for
> example log1 -> log2 -> log1, will cause log1 to be overwritten.
> This can simply be documented, since it is not a particularly
> surprising behavior.
> 
> Suggested-by: Alex Bennée<alex.bennee@linaro.org>
> Signed-off-by: Paolo Bonzini<pbonzini@redhat.com>
> ---
>   util/log.c | 13 +++++--------
>   1 file changed, 5 insertions(+), 8 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~